A novel mechanical analogy based battery model for SoC estimation using a multi-cell EKF

TL;DR

This paper introduces a mechanical analogy-based battery model and a multi-cell EKF approach for improved State of Charge estimation, enhancing battery management systems in energy storage applications.

Contribution

It presents a novel cell model using electric dipoles and a multi-cell EKF system for accurate SoC estimation, relying solely on voltage and current measurements.

Findings

Encouraging SoC estimation accuracy with prototype tests

Effective multi-cell tracking with round-robin EKF approach

Model captures voltage dynamics through electric dipoles

Abstract

The future evolution of technological systems dedicated to improve energy efficiency will strongly depend on effective and reliable Energy Storage Systems, as key components for Smart Grids, microgrids and electric mobility. Besides possible improvements in chemical materials and cells design, the Battery Management System is the most important electronic device that improves the reliability of a battery pack. In fact, a precise State of Charge (SoC) estimation allows the energy flows controller to exploit better the full capacity of each cell. In this paper, we propose an alternative definition for the SoC, explaining the rationales by a mechanical analogy. We introduce a novel cell model, conceived as a series of three electric dipoles, together with a procedure for parameters estimation relying only on voltage measures and a given current profile. The three dipoles represent the quasi-stationary, the dynamics and the istantaneous components of voltage measures. An Extended Kalman Filer (EKF) is adopted as a nonlinear state estimator. Moreover, we propose a multi-cell EKF system based on a round-robin approach to allow the same processing block to keep track of many cells at the same time. Performance tests with a prototype battery pack composed by 18 A123 cells connected in series show encouraging results.